The DNR is planning a study to determine if breakwaters reduce erosion in a large lake. They are dividing the shoreline into 100-foot sections, installing breakwaters in some and leaving others as they are. However, due to prevailing winds, the east and west shorelines experience distinct wave patterns. Consequently, the DNR anticipates that these conditions will influence the effectiveness of the breakwaters. Thus, they plan to consider each shoreline as a separate group in their analysis. This study is an example of:a. an uncontrolled experiment b. a blocked design experiment c. a matched pairs experiment d. a stratified random samplee. a randomized observational study

b. a blocked design experiment

In this study, the Department of Natural Resources (DNR) is planning an experiment where they are comparing shoreline sections with breakwaters to those without breakwaters to see if they reduce erosion. They are also taking into account the differences in wave patterns on the east and west shorelines by considering them separately in their analysis. This separation into different groups based on a specific characteristic (in this case, the distinct wave patterns) that is expected to affect the outcome of the experiment is what defines a blocked experiment.

Blocking is used to reduce the variability within an experiment that is not due to the treatment itself but due to other extraneous factors (in this case, the direction of the shorelines relative to prevailing winds). By comparing the breakwaters effect within these blocks (east and west shorelines), the DNR is attempting to isolate the impact of the breakwaters on erosion from the impact of wind pattern differences.